Galactose oxidase from Dactylium dendroides catalyzes the two-electron oxidation of primary alchohols to aldehydes. The enzyme contains a copper ion cofactor and a unique tyrosine-cysteine dimer, the thiol group of C228 is covalently linked by a thioether linkage to the ortho position on the phenol side chain of Y272 replacing a hydrogen atom on one of the ortho ring carbons. X-band EPR and ENDOR spectroscopic studies have previously identified this dimer as a free radical site. High frequency EPR spectra of the free radical and a model 2-methylthiocresyl radical reveal virtually identical g-values. The nearly axial g-tensors provide corroborating evidence for a covalent thioether linkage and indicate that spin density is strongly localized on the cresol/tyrosine and sulfur rather than being delocalized throughout an extended p-network. Thus effectively eliminating the possibility that the enzymatic free radical is delocalized over the three amino acids Y272, C228, and W290 in a hypothesized extended p-network. High frequency EPR also reveals a distribution in the largest g-value of the model para-cresyl radical not detected at conventional frequencies.